In patients with knee osteoarthritis, as the tibiofemoral forces increase, knee pain can increase significantly. It is therefore of value to reduce the tibiofemoral forces on the knee joint during ambulation over a variety of surfaces and terrains.
A number of orthotic devices have been designed to reduce tibiofemoral joint forces and alleviate pain associated with joint movement, and sometimes to rehabilitate the joint over time.
For example, Nace, in U.S. Pat. No. 8,057,414 discloses and claims an offloading brace that is designed to relieve pressure on either the medial or lateral side of the tibiofemoral joint. In addition, there is employed a “spring loaded adjustable fulcrum” to assist in leg extension after the knee is flexed. However, while different amounts of spring torque may be introduced by adjusting the mechanical spring settings before the brace is donned, there are no means for modifying the spring torque while being worn or programmably as a function of knee angle. Moreover, there are no means for locking the spring in compression and releasing the spring at a selected angle during ambulation.
As a further example, in U.S. Pat. No. 6,010,474, Wycoki discloses a leg orthotic device that is said to offload tibiofemoral forces on the knee joint bilaterally. In addition, the disclosed orthotic device is said to relieve pressure on the patellar compartment. There is also disclosed a spring assembly for “biasing the knee toward extension.” The pressure on the knee joint is said to be offloaded by “transferring the pressure through the strut assembly to the thigh” using straps and an inflatable thigh cuff. However, while different amounts of spring thrust at heel strike may be introduced by adjusting the mechanical spring settings before the brace is donned, there are no means for modifying the spring thrust while being worn or programmably as a function of knee angle. Moreover, there are no means for locking the spring in compression and releasing the spring at a selected angle during ambulation.
In U.S. Pat. No. 7,393,335, Carvey et al., incorporated herein by reference, disclose a knee brace that provides support for the torso via the hip and increases leg thrust. However, Carvey et al. do not provide a method of programmably modifying the torque from the spring beginning at a programmable angle during knee flexion and releasing the spring at a programmable angle during knee extension.
Therefore, there remains a need for a biomechanical leg orthosis that, during ambulation, provides a programmable means for storing energy while the knee is flexing and a means for programmably releasing the stored energy when the knee is extending. Moreover, there remains a need for an improved leg orthosis that begins storing energy at a selected angle of knee flexion angle after heel strike. These needs are addressed by the subject matter disclosed and claimed herein.